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Pressure relief and disposal of elastic strut thrust bearings
Source: Bearing network time: 2014-10-26
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Before the equipment leaves the factory; the manufacturer vacuums the entire elastic fuel tank group; the residual pressure is 5mmHg column height; then it is filled with 30# turbine oil; the check valve is installed on the two oil ports installed in the symmetrical direction of the elastic oil tank group. Oil-holding pressure. To ensure that the elastic fuel tank does not relieve pressure; a hemispherical solid steel cover is welded to the outside of the check valve; this layout ensures that even if the check valve sees oil leakage, the oil leakage will not exceed 100ml. (The leakage exceeds 100ml; the elastic tank is ineffective.) Before the elastic tank of the manufacturer is pressurized; set its height to zero; when the internal charge pressure is from 0 to 1.1 MPa; the rise of the corrugated oil wall is measured. Not more than 1mm; at this moment; the corrugated wall stress of the elastic fuel tank is 440MPa; then it is simulated to load the 3100T on the elastic oil tank group formed by 18 fuel tanks; the tank tightening value is about 0. 80mm.
2 The pressure relief of the elastic oil tank is judged one month before the leakage of the fuel tank; the operating personnel reflect that the temperature of the thrust tile of the No. 3 turbine generator set has changed greatly; the records are viewed from the relevant inspections; the recorded data also reflect the obvious change of the Wawen. The temperature difference of each tile is 5~10°C. At that time; check the oil level of the unit is normal; the cooling water pressure is normal; but the pendulum of the unit is increased. Check the record of the overhaul of the machine on November 3, 1993; Within the scope of qualification; it is close to the program minor repair; therefore, as a problem; to be specifically reviewed when minor repairs.
October 1994; we carried out minor repairs to Unit 3 according to the plan; and conducted a detailed review of the thrust bearings:
(1) Measure the spacing between the thrust pad and the working surface of the mirror plate:
Compare the record of the minor repair on October 3, 1994 with the record of the overhaul on November 3, 1993; it can be seen that the elevation of the thrust bearing has dropped by nearly 2 mm; the bolt of the thrust strut is not loose. Therefore, it can be concluded that the elastic tank is leaking. The pressure constitutes the drop of the thrust bearing elevation.
(2) Check the lower edge of the elastic oil tank cover with a feeler gauge. Find the leak point and make up the oil pressure in the elastic fuel tank group to find the leak point. First, fill the elastic oil tank with 1. 1MPa turbine oil; Check the leak point under the condition. The elastic fuel tank is first vacuumed at the factory; then it is filled with oil and pressurized; for this purpose; the oil filling and pressurization must ensure the hygiene of the pipeline and oil;
The process of charging review:
Void:
Comparing from the gap value of the cover; we can see that the tightening value of the fuel tank is about 2mm when the force is not affected by force; according to the maintenance experience and the manufacturer's demand; the tightening value of the elastic tank should be within 0. 50mm when the force is applied. The current tightening value is 2mm; the practice reflects the tightening value of the corrugated wall under the pressureless condition of the elastic fuel tank.
Based on the above situation, we can draw the following conclusions:
The obvious change of the Wawen is due to the pressure relief of the elastic tank group; the hydraulic failure of the thrust bearing; the hydraulic elastic strut thrust bearing; the rigid strut thrust bearing; under the operating condition of the unit; Uneven; and produced a significant change in the temperature difference between the tiles.
.1) Use a welding to blow a hemispherical steel cover weld between the two check valves of the elastic tank group. (The stainless steel cannot be cut due to the oxyacetylene flame).
.2) Set the charging line; and should meet the following requirements:
Use 30# turbine oil; the oil source comes from the governor oil pressure equipment,
Use a pressure gauge with a measuring range of 6 MPa.
Pipes, valves, pressure gauges and pipe joints are required to be hygienic; and there is no leakage through the pressure test.
.3) After the pressure oil from the governor oil pressure device is depressurized; (valve control); flush the pipeline; take out the plug on the check valve together; connect the pipeline with oil.
.4) gradually open the valve II; when the indication in Table II is 1. 5MPa; close the valve II; then gradually open the valve I; to be indicated by the table I is 0. 2MPa when the valve is closed.
.5) use a high-pressure oil pump to lift the rotor; the pressure of Table I is not seen; repeat the operation; until the pressure is 1. 1MPa.
.6) After installing the measuring rod and the dial indicator for adjusting the force on the cover, gradually lower the rotor.
.7) Check that the pressure in Table I is still at 1.1 MPa; (the check valve is actively closed) to see that the elastic fuel tank body and each fuel tank receive the weld without leakage; the equipment thread of the check valve on the elastic fuel tank is found to be oily; A check valve is welded to the weld of the steel cover. It is found from the reading on the dial gauge; the change in time and the change in the amount of leakage; the reading is also changed; thus the elastic tank pressure relief is the check valve. The thread buckle is oily and the oil leakage of the steel cover does not guarantee the effect.
After the elastic oil tank leaks and leaks, we use the A102 stainless steel welding rod produced by Pingxiang Electric Welding Rod Factory to weld the check valve of the check valve; the other steel cover welds are also repaired.
After the disposal; the second filling is still carried out according to the charging process; and the welded joint of the steel pipe is connected to the elastic oil tank; the check screw thread weld and the outer welding of the steel cover are coated with white chalk. After the rotor is dropped; The thrust bearing accepts some components under the weight of about 1100T; the pressure is 36h. After viewing; the white chalk powder is all dry; according to the thrust tile force adjustment method; each rise and fall three rotors; the percentage of each elastic tank The reading of the table is stable and has no obvious change. The force of the thrust pad to the working surface of the mirror plate is measured under the force condition; it has reached the record of the overhaul in November 1993.
After disposal, there is no leakage in the elastic fuel tank group; therefore, we have processed a steel cover from the beginning; to prevent future leakage; fill the steel cover with 504 glue cement; then use A1O2 electrode; weld the steel cover from the head Check valve outside.
4 points advocate elastic column type thrust bearing; also called hydraulic strut type thrust bearing; it is the principle of using hydraulic connecting device; the elastic oil tank of each thrust tile is connected with steel pipe. Therefore, the force of each thrust tile can be active Adjustment; it has higher bearing capacity; it is widely used in hydro-generator units with thrust load greater than 1000tf. However, once it loses pressure, the thrust bearing in operation is transformed into rigid-strut thrust bearing; its bearing capacity Decrease; the thrust tile is not evenly stressed; the unit's temperature rises; the swing and oscillation increase; affect the safe operation of the unit. For this reason: the unit with elastic fuel tank; every time the large and small repairs should be viewed the elastic tank Leakage condition. Together; when the unit is running; found that the temperature of the tile changes significantly; should stop at the collector ring to measure the elevation of the fixed component and the transition component; and record; to determine whether the elastic fuel tank can be relieved.
Especially at present; most large-scale units have replaced Russian-made elastic metal plastic tiles; their plastic layers have a heat-insulating effect; the change reflected on the temperature of the tile is higher than that of the gray (11). Every noisy drag is not enough.
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